If you're SE and you'd rather support an independent shop, Water Into Beer in Brockley should have pectolase and and any other supplies you might need.
Sadly I'm in deepest darkest Berkshire so Wilko's will have to do. Although my local hardware store does have some brewing supplies I haven't seen pectolase.
If you're SE and you'd rather support an independent shop, Water Into Beer in Brockley should have pectolase and and any other supplies you might need.